Cooling system for the head portion of pistons of high-speed internalcombustion engines



Nov. 3, 1953 K. MAYBACH 2,657,678

COOLING SYSTEM FOR THE HEAD PORTION OF PISTONS I OF HIGH-SPEED INTERNAL-COMBUSTION ENGINES Filed Aug. 11, 1951 2 Sheets-Sheet 1 Fig.1 20 Z I i i k 2" l J3 Zmventor KARL MAYBACH attorney Nov. 3, 1953 K. MAYBACH 2,657,678

COOLING SYSTEM FQR THE HEAD PORTION OF PISTONS OF HIGH-SPEED INTERNAL-COMBUSTION ENGINES Filed Aug. 11, 1951 2 Sheets-Sheet 2 INVEN TOR KARL MAVBACH ATTORNEY Patented Nov. 3, 1953 COOLING SYSTEM FOR THE HEAD PORTION OF PISTONS OF HIGH-SPEED INTERNAL- COMBUSTION ENGINES Karl Maybach, Friedrichshafen (Bodensee) Germany, assignor to Maybach-Motorenbau G. in. b. H., Friedrichshafen, Germany, a German Application August 11, 1951, Serial No. 241,448

Claims priority, application Germany September 9, 1950 9 Claims.

The present invention relates to cooling systems for the head portion of pistons of highspeed internal combustion engines, more particularly to systems in which a coolant is pumped through a cooling chamber in the head portion of the power pistons by the pump action produced by stationary coolant supply and removal tubes whose ends telescope with coolant supply and removal conduits in and reciprocating with the power piston.

The piston diameter and consequently the power output of high-speed internal combustion engines, particularly as used in motor vehicles, is limited primarily by the temperature of the piston head. The piston diameter can be considerably increased if appropriate cooling, particularly by coolant supplied under pressure through pumping tubes, is provided, the coolant being the oil as used in the crankcase of the engine. Because of the pump action of the tubes, arrangements of this type depend on the engine speed, and usually much more cooling oil is supplied to the piston head than needed. Because of the unfavorable proportion between piston stroke and diameter of the pumping tubes, the oil pressure in the cooling chamber is too great at the conventional high speeds for which the engines are built. During the suction stroke of the pumping tubes, the pressure in the cooling chamber is so much reduced that the flow of oil is interrupted, oil vapor alternates with liquid oil, and air enters the cooling conduits resulting eventually in the formation of undesired foam.

These are the reasons Why piston cooling systems as described above, though successful in low-speed engines, could not be applied to highspeed engines.

It is an object of the present invention to provide a cooling system comprising pumping tubes for the pistons of high-speed internal combustion engines which system is independent of the speed of the engine and applicable to engines operating at very high speed.

A further object of the invention is to reduce the undesired pumping effect of the pumping tubes of piston cooling systems of high-speed internal combustion engines and to avoid undesired high and low pressures of the cooling oil in the piston cooling chamber. This is accomplished by providing equalizing means in the piston cooling systems, which means receive a portion of the cooling oil during the pumping stroke of the piston and release it during the opposite stroke. These means comprise preferably one or more spring-actuated equalizing pistons or diaphragms which are exposed to the pressure of the cooling oil in the cooling chamber of the piston. Stroke and bore of the equalizing pistons and their cylinders, and the pressure of the springs acting on the pistons against the pressure of the coolant, are so arranged as to produce the desired effect on the oil pressure in the cooling chamber. The stroke of the equalizing piston is short relative to its diameter, and the relation between stroke .and diameter of the equalizing piston is the in- .verse of that between the stroke of the power piston and the diameter of the pumping tube, the latter being very small compared with the stroke of the power piston. By proper selection of the pressure of the spring acting on the equalizing piston, the output of the pumping system can be adjusted for best results.

No special valves are needed for controlling the fiow of the cooling oil in pistons according to the invention; an oil supply pump may produce the desired effect. A check valve, however, is provided for controlling the flow of oil entering the tube which admits cooling oil into the cooling 'chamber.

Preferably, the oil flows from the cooling chamber through an outlet tube, and a valve may be provided in the conduit receiving the oil from said outlet tube for closing the oil outlet if the oil pressure in the cooling chamber is below that in the outlet conduit. Without provision of pressure equalizing means according to the invention, such valves would have undesirably large flow areas in high-speed engines. If the abovedescribed equalizing means are provided, only a portion of the oil moved by the pumping tubes need be passed through the valves, and the flow area of the latter need not be much greater than lthat of the tubes.

With the arrangement according to the invention, the pumping effect of the tubes is generally sufficient to produce the desired oil flow through the cooling chamber. The oil supply pump, ii 'such is provided, need only be large enough to 'replace the oil which is lost through leakage.

The invention is particularly applicable to pistons comprising a main body and a head member having cooling passages. The equalizing piston according to the invention is guided in a bore .of the main body, the head of the equalizing piston forming part of the wall of the cooling chamber in the center ofthe power piston. Preferably a protuberance is provided in the center of the power piston for guiding the equalizing piston, oil flowing through said protuberance to the wrist pin bearing for lubrication of the latter. I

Other objects will appear from the following description. of this invention.

The manner inzwhichthe foregoing objeot's. are achieved is shown in the appended drawings, wherein throughout the several views, and in which:

Fig. 1 is a longitudinal sectional'viewofa"power piston and part sectional view of' the cooling oil circulating system according to the invention;

Fig. 2 is a longitudinal sectional View of. the

upper part of a modified piston according. to. the invention;

Fig. 3 is a longitudinal sectional view of a further modification of the head portionoi a piston.

according to the invention, the section being taken along line III-411 in Fig. 4.;

Fig. 4 is a top view of the piston illustrated in Fig. 3 with the head part removed.

Referring more particularly to Fig. I, numeral l designates a piston having a cooling chamber 2 in which an oil supply tube 3 terminates. A- stationary tube 5 extends substantially coaxially into the lower part of tube 3; Substantially diametrically opposite supply tube 3 is an outlet tube 5' for removing theoil' from chamber 2". The lower end of tube 5 moves along a stationary'tube 6, the latter being coaxial within theformer; Tubes 4 and 5 are individually connected with substantially T-shapedconnecting parts- I and 8, respectively, the fornier'receiving oil from a supply pump 9 through conduit 9 and the latter discharging into conduit I0. Conduit II' on connecting part T conducts oilto another piston of the engine, and conduit I2 receives oil w from another piston. A spring-loaded check valve I3, I5 is arranged in the connecting member 1 for the coolant supply conduit 4 and a spring-loaded check valve I4, HS in the connecting member 8 for the coolant discharge conduit 6.

An equalizing piston is received in bore 2I in the upper'pa'rt of the wrist p'in support part of the piston and coaxial of the latter, piston 20 closing the bore against the cooling'chamber' 2. A spring 22 resting on plate 23 presses piston 20 against the pressure in chamber 2; Plate 23 has marginal portions inserted in recesses 24 of ribs 25 provided in the interior of the power. piston I for supporting the wrist pin.

Cooling oil is supplied. by pump 9' in. conduit 9. During the up-strol ze of piston I, oil flows from conduit 9 through connectorl, valve I3, and tube 4, into-tube. 3, which terminates incooling chamber 2. The volume made available in conduit 3 during an up-stroke of piston I is larger than the volume. of the oil. supplied by pump 9 to conduit 9, and; since no oil can escape through conduits 5, 5' and I'll because of the check valve I4 in connector 8, the pressure in chamber 2 is reduced and piston 20 forced thereinto by spring 22 to compensate the difference between the.- increase of available space and the volume of the oil supplied. by pump 9'. If. the pressure in chamber 2 falls below atmospheric pressure, the latter supplements-the action of spring 22.

Downward movement of piston I causes increase of pressure in chamber 2 and closing of valve I 3, and oil, which ha'sibeen forced into conduits 3 and 4 during the upstroke of'the piston, enters chamber 2. At the same time, a certain amount of cooling oil leaves chamber 2 through conduits 5 and a, valve 54, connect0r8, and conduit I0. Equalizing piston 20 is moved outward by the increased pressure in chamber 2. The pressure in chamber 2 decreases during an upstroke of piston I and increases du i g a do nlike numerals designate like parts.

4 stroke; these changes of pressure during the flow ofcooling. oilthrough. chamber 2, however, are limited by the provision of pistonlfl, the equalizing effect of the latter depending on the power of spring 22 and the size of the piston. The diameter of the latter is at least as great as its stroke. in most. cases substantially greater.

In themodification shown in Fig. 2, the power piston consists of a-main body 3| and a head part 3.2 havinginternalcooling ribs 33 forming conduits. or channels for the cooling oil. The main body 3-I: hassaniaxia'l bore 35 receiving an equalizing piston 34. The: head part 32 is provided with an internal, axial, tubular extension or guide means 36', projecting downwardly and through a.huhpart. 3.1; of piston 34. Piston body 3| is provided with an annular projection 38 extending radially inward for supporting springs 43 which extend into the annular recess formed in the underside of pist0IL34 by the hub portion 31. Springs 43' press the annular piston. 34 against thecentral. ribs 33 closing: the central cooling channel'sv 30: when. the spring-loaded. piston 34 overcomes the pressure. ofIt'he coolant in the cooling channels. The lower end of the interior 39 of guide 36 is closedzby a cover 40 having an aperture 4|. Transverse. bores. 42 in the upper part of extension 36 connect the interior 39 with the coo'ling'chamb'er'30.

The cooling oil is admitted to' cooling chamber 30 through a conduit. 3' and relieved through conduit 5-" inthe same manner and the function of the device is the same as in the embodiment according to Fig.1". A. small part of the cooling oil flows from cooling chamber 30 through bores 42, chamber 39,. bore 41', into a bore in the wrist pin bearing end 44 or the piston connecting rod for lubricating the wrist pin bearing.

Figures 3 and 45 illustrate a modification of the piston cooling system according to the invention having a plurality of. equalizing pistons. The power piston comprises aamain part 58 and a head part- 51 which is bolted to the former by bolts 52. Cooling 011' is supplied through conduit 3 to the cooling chamber 53 inthe interior of the head part 5I' the same manner as in the embodiments shown in- Figs.- land 2 and is relieved from the cooling chamber through aconduit 5". The head part 5 I is provided with internal cooling ribs 54 projecting into-the cooling chamber.

A-n insert 55 in main part of the power piston has three cylindrical recesses 56,51, and 58, accommodating pistons 56 51, and 58., respectively. These pistons are forced upward into the cooling chamber 53 by'springs 59, 60', and GI, respectively. Apertures 62; 63, and 64 are provided in the bottom of insert for connecting. the chambers 56; 51, and 58,. respectively, with" the outside.

While the preferred: embodiments of this invention are: shownan'd described, modifications other than those discl-osedherein may be made without departing from the: spirit of: the invention, and reference is therefore made tothe appended claims for a definition ofthescope of this invention.

I claim:

1.. A compensated cooling system for the head portion of a. power piston for high-speed internal combustion engines, comprising a cooling chamber disposed in the head portion and being completely cl'osed' against the cylinder in which the iston operates, coolant circulating conduits connected and reciprocating with the power piston and terminating in said cooling chamber, stationary coolant supply and removal tubes individually extending into said conduits, and compensating means connected with said piston and communicating with said chamber and being adapted to be actuated by the coolant pressure in said chamber and to compensate, at a predetermined rate, the fluctuations of coolant flow through and of coolant pressure in said chamber caused by the pump action of said conduits and of said stationary tubes.

2. A cooling system as defined in claim 1, said compensating means comprising a movable member forming a movable wall portion of said chamber and being adapted to decrease the internal volume of said'chamber upon an up-stroke of the power piston and to increase the internal volume of said chamber upon a down-stroke of the power piston.

3. A cooling system as defined in claim '1, said compensating means comprising a piston chamber connected and communicating with said cooling chamber, an equalizing piston in said piston chamber, and a spring resting on the power piston and on said equalizing piston for pressing the latter against the pressure of the coolant in said cooling chamber.

4. A system as set forth in claim 3, the diameter of said equalizing piston being at least as great as the stroke of the equalizing piston.

5. A system as set forth in claim 3, said piston chamber being disposed coaxially of the power piston.

6. A compensated cooling system for the head portion of a power piston for high-speed internal combustion engines, comprising a cooling chamber disposed in the head portion and being completely closed against the cylinder in which the piston operates, coolant circulating conduits connected and reciprocating with the power piston and terminating in said cooling chamber, stationary coolant supply and removal tubes individually extending into said conduits, a check valve in each of said stationary tubes, and compensating means connected with said piston and communicating with said chamber and being adapted to be actuated by the coolant pressure in said chamber and to compensate, at a predetermined rate, the fluctuations of coolant flow through and of coolant pressure in said chamber caused by the pump action of said conduits and of said stationary tubes.

7. A compensated cooling system for the head portion of a power piston for high-speed internal combustion engines, comprising cooling channels disposed in the head portion and being completely closed against the cylinder in which the piston operates, coolant circulating conduits disposed within and connected and reciprocating with the power piston and communicating with said channels, each of said conduits comprising a straight part parallel to the longitudinal axis of the power piston, stationary coolant supply and removal tubes individually extending into said straight parts, a main piston part connected with the head portion of the said power piston, a piston chamber coaxial of and within said main piston part and communicating with said channels, and a spring-loaded equalizing piston in said piston chamber.

8. A cooling system for the head portion of a power piston for high-speed internal combustion engines, comprising a coolant, a cooling chamber in the head portion of the power piston, coolant conduits in and reciprocating with the power piston and terminating in said cooling chamber, stationary coolant supply and removal tubes individually extending into said conduits, a piston chamber extending from said cooling chamber axially of the power piston, a piston rod having a wrist pin bearing end, a tubular guide means connected with said head portion, extending through said piston chamber coaxially of the power piston, and terminating adjacent to said bearing end, an amiular equalizing piston in said piston chamber and disposed around said guide means, and spring means resting on said power piston and on said equalizing piston for pressing the latter against the pressure of the coolant in said cooling chamber, said coolant being a lubricating oil and the interior of said guide means communicating with the cooling chamber and receiving oil therefrom and discharging it on said bearing end.

El. A compensated cooling system for the head portion of a power piston for high-speed internal combustion engines, comprising a cooling chamber in the head portion of the power piston, coolant conduits within and connected and reciprocating with the power piston and terminating in said cooling chamber, stationary coolant supply and removal tubes individually extending into said conduits and pumping coolant through said cooling chamber upon reciprocation of the power piston, compensating means connected with the power piston and communicating with said cooling chamber for compensating the fluctuations of coolant flow through and of the coolant pressure in said chamber at a predetermined rate, and a coolant supply pump connected with said supply tube for maintaining said supply tube filled with coolant at all operating conditions of said system.

KARL MAYBACI-I.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,241,629 Brill May 13, 1941 FOREIGN PATENTS Number Country Date 547,111 Great Britain Aug. 13, 1942 265,555 Germany Oct. 9, 1913 272,054 Germany Mar. 23, 1914 723,470 France Jan. 18, 1932 

